Liquid level indicator



May 21, 1935. c. 1.. SEWARD, JR

LIQUID'LEVEL INDICATOR Original Filed Deb. 14, 1952 2 Sheets-Sheet 1 CONNECT T0 POINT OF STATIC PRESSURE T0 ENGINE OR FUEL PUMP INVENTOR. C/arence L. Jewara', if

ZW ATTORNEY.

45 The-above and-other objects and advantages Patented May 21, 1935 i UNITED STATES PATENT OFFlC LIQUID LEVEL INDICATOR Clarence Lee Seward, (In, Washington, D. 0., as-

signor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Original application December 14, 1932, Serial No. 647,290. Divided and this application June 9, 1934, Serial No. 729,857

4 Claims. (CI. 73-54) The present application is a division of my a being had for this pu p to ithe pp corpelldihg application Serial No..647,290, filed cleims- December 14, 1932, and the invention herein dis- In th drawin s wherein like reference ha closed relates to liquid level indicators f th acters refer to like parts throughout the several remote type such, for example, as are disclosed Views: in U. s. Patents Nos. 1,711,506 and 1,711,507 is- 1 ll t ates a al section taken 5 sued to Morris M. Titterington on March 7, 1929, through the liquid level indicating device. and more particularly, the invention refers to th t n v v ntin va of th t nmeans for preventingliquid from entering the through t e supply tank, a d shOWing the indicator from the-supply ta k hil providing connections between the three elements men- 10 a common venting connection for the indicator timed; and for the supply tank with which it is asso- 2 is a nt l vat f th ind atin ciated. device;

One of the objects of the invention is topro- 3 i a al Section Of One form o Ventvide, in combination with a liquid level indicator, ing valv m dy n the inventi n;

novel venting means for the indicator and the 4 s & seetionaLview of another m of container or tank with which it is associated valve embodying the ve t on; whereby, under certain extreme conditions, liquid 5 is a View similar to g- 4 Showing the is prevented from entering the indicator from manner of Operation of e Valv p actua ion the container or tank, of the pendulum by either acceleration forces, Another object is to provide, in a device of the centrifugal forces. a ty; class described adapted to b mqunted on Fig. v6 is a vertical sectionof still another form hicle and having a common venting connection of Pendulum controlled Valve in its actuated D from the supply tank and the indicator to the sitien; atmosphere or to some suitable point of static 7 is a similar View showing the a ve o pressure, novel means whereby the connection 6 in normally p position; between the tank and the indicator is automati- Fi 8 is a t ans e section taken along th cally closed upon acceleration of the vehicle or line 8 0f e' and upon inclination thereof in any direction with Fig is a det Perspective of One Of the 30 respect to the horizontal so that liquid from the elementsof the valve shown in Figs. 6, 7 and 8.

supply tank is prevented from entering the indi- Referring more particularly to Fig. 1 of the 30 cator. drawings, the liquid level indicating device or A further object of the invention is to provide g t co p ses a casin a flex b e dianovel means, in combination with a liquid fuel phragm device l2 whic is esp s p level indicator of the hydrostatic type particusures transmitted thereto from the tank I3 by larly adapted for use on aircraft, whereby the means f a hydr stat s ll a d h p p nfuel supply tank and the indicator may be vented neotion en s of e p essu spont a, common remote point while preventing sive device 12 are transmitted to a pointer IS in sage of fuel from the tank to the indicator upon suitable manner as by means of a link 40 acceleration of-the aircraft or upon departure Whlch 1s m1eci1edt0 he rack lflpivotally mountthereof from normal level flight, without stopd and adapted to mesh witha'pmion the ping the supply of fuel to the engine of the airh f f g gg ggzg ff g ggg g gif iizg g g ggf z g aircraft 18 (16' carried by and at the front of the casing. Associated with the pointer i6 is a dial 23 for the 5 of the invention will appear more fully hereinfiga g z ii g gfidligatinlse gigiigzirlelvieig 311: after with reference to the detailed description dial 23 may be covered'by a mmber 25 of some t which follows, when taken in connection with suitable transparent material preferably um the accompanying drawings whel'einseveml breakable, such as celluloid, and supported in a bodiments of the invention are illustrated. It is f am gt to be expressly understood, .however, that the A iated withthe gage III is a pump 21 which I d aw n s a for the P p illustration and comprises a cylinder 28 and a piston 29 reciprodescripti n nly a d are t d s n d as a d flcally mounted therein, the latter being in the nition of the limits of the invention, reference form of a flexible cup carried at one end of the rod 30. At the other end of the rod 30 there is provided a knob 3| for the purpose of manually operating the pump by pulling said cup outwardly against the compression of a spring 32 surrounding the rod 30 and interposed between. the piston 29 and a wall of the cylinder 28. An opening 33 is provided in the cylinder for admitting air thereto on the outward stroke of the piston 29. Normally the piston 29 abuts the end wall 34 thereby maintaining the passage 35 closed with respect to the cylinder 28. The gage and pump are adapted to be mounted on an instrument panel (not shown) of a vehicle such as an aircraft, automobile, and the like.

The interior of the gage casing H and the top of the supply tank l3 have a common venting connection to the atmosphere at some suitable remote point by 'means of a T-connection 36, one endof which is connected to the tank l3 by means of a pipe 31, and the other end of which is connected to the point of static pressure (not.

shown) by pipe 38. The interior of the gage casing II is connected to the T by means of a pipe 39 through the novel venting valve. 40 which is normally open and which will be described more fully hereinafter. The tank l3 may be carried on any suitable support shown generally at M and constituting a part of the vehicle on which the indicator I0 is adapted to be carried and is provided with a filling opening 42 which is closed by a threaded cup 43. A supply pipe |3a is connected to the bottom of the tank l3 for supplying fuel directly to the engine of the vehicle or through a fuel pump when forced feed is employed. p

The operation of the liquid level indicating device It] as a simple hydrostatic gage is as follows:

Assuming that there is no liquid in the tank l3 and initially the system,. including the tank, is full of air, then as liquid is poured into the tank l3, it rises in the hydrostatic cell M and compresses the air contained in the cell and in the pipe IS in accordance with the hydrostatic head of the liquid. This pressure is then transmitted to the gage through the pipe l5 and to the pressure-responsive member l2 which causes the operation of the pointer 16 by means of the shaft 2|, pinion 20 and rack 18. The dial 23 of the gage may .be.. calibrated so that it will indicate the level of :thliquid in inches, gallons, pounds or some other function of pressure-head as may be desired.

If the maintenance of a constant amount of air in the system 'could be assured, the gage would continue to indicate the level of the liquid correctly at all times. It has been found, however, that various factors contribute to making it difficult or practically impossible to maintain the air in the system without auxiliary means. Changes in temperature, changes in pressure,

.minute leaks and other effects tend to reduce the amount of air in the system and thereby reduce the indication of the gage and render it undependable as a quantitative indicator of the liquid level. Means are, therefore, provided for replenishing the air in the system to compensate for losses due to the factors recited, said means comprising the pump 21.

The cooperative function of the pump 21 with the gage I0 is as follows:

When it is desired to ascertain accurately the liquid level in tank l3, it is necessary to expel all liquid from the pipe l5 and cell H. The piston rod 30 of the pump is, therefore, pulled outward to the right as viewed in Fig. 1, and then released so that the spring 32 causes the piston 29 to be pushed back to its normal position so that it abuts the wall 34 and closes the passage 35. On the outward stroke of the piston rod 30 the flexible cup 29 permits flow of air around its periphery 10, which air is admitted into the cylinder through the opening 33. On the return stroke the cup expands against the walls of the cylinder and prevents the escape of air past it. The air is, therefore, delivered through passage 35 into the pipe l5 and is blown out of the bottom of the hydrostatic cell M thereby clearing the system of liquid and providing sufficient air within the pipe l5 for the transmission of the hydrostatic head of the liquid 24 to the pressure-responsive member l2. The indication of the gage following this clearing of the pipe-line I5 and cell it and the replenishing thereof with air, will be the correct level of the liquid in the tank.

Heretofore, it had been the practice to merely leave the tank l3 and the gage casing ll open to the atmosphere by an aperture provided in each for proper venting thereof without any connection therebetween. Such an arrangement functioned satisfactorily when employed on automobiles where the static pressures at the gage and at the tank are substantially the same. In aircraft, however, such as airplanes, particularly planes provided with wing tanks, considerable difficulty was experienced with hydrostatic gages due to the differences in staticpressure within the gasoline tank which is vented to the exterior of the plane, and in the gage which is generally located on the instrument panel in the cockpit of the plane. Therefore, a liquid level indicating gage, such as a gasoline gage, would indicate differently with the aircraft in flying position on the ground (i. e., the tail propped up to give the tank a true horizontal position for calibrating the tank and gage) and with the aircraft in actual flight, due to additional pressure being introduced into the tank produced by wind velocity exterior of the plane when the latter is in flight. It is, therefore, essential that the gasoline gage be vented to the same place as the tank and preferably to some suitable remote point of static pressure, although the particular point of connection may be at some velocity pressure without making any substantial difference, since no difierence in pressure will result so long as the tank and the gage are connected to the same point. To this end the present invention provides novel means for providing a common connection from the gage and the tank to some suitable remote point (not shown) as, for example, to a Pitot-static tube carried on the leading edge of the wing of an aircraft, said means being effective upon acceleration of the aircraft or upon departure thereof from normal flight, to close the connection between the tank and the gage for preventing the passage of the liquid fuel from the tank to the gage while permitting the feeding of the liquid fuel to the engine of the aircraft as, for example, when the aircraft is deliberately put into a power dive, at which time the acceleration forces are excessive. The device consists generally of a vent valve adapted for connection in the pipe-line constituted by pipes 31, 38 and 39, said valve comprising a body portion having means thereon for connecting it into said pipeline, means forming a. passage through said body portion and means including, a universally mounted pendulum suspended from the body portion to close said passage upon movement of said valve adapted for use in accordance with the invention is illustrated, said valve comprises a tubular body portion 44 provided with external threads 45 and 46, respectively, at each end thereof and with a hexagonal nut portion 41 in order that a suitable wrench may be applied thereto for securing the valve in the pipe-line by means of coupling members which are adapted to engage the valve by means of the threads 45 and 46. The valve has a passage 48 extending therethrough which is restricted at the lower end of the-valve by means of a bushing 49, the

latter having an annular flange'lll and may be press-fitted within the passage 49 near the lower end thereof and which has a relatively narrowpassage 5| therein. Associated with the bushing 49 and cooperating with the lower end thereof is a spherical member or ball 52 which is seated on an annular supporting member 59 having a central opening 54 and being secured within the lower end of the valve by means of external threads 55 which engage with internal threads 56 provided on the inside of the valve. The spherical member or ball 52 is provided with a relatively small passage 51, terminating in a pair of diverging passages 58 and 59, respectively. Secured to or formed integral with the ball 52 is a rod 60 having at its other end a weighted mass M which con titutes a pendulum having a universal support formed by the ball 52 which is seated within a spherical seat 52 provided on the upper side of the supporting member 59. Hence the pendulum 6| is adapted for universal movement in any direction with respect to the vertical axis of the valve. When the pendulum 6| and the valve 40 are normally in vertical position, the passage 51 in the ball 52 is in alignment with the restricted passage 5i so that a clear path is provided through the body portion 44 of the valve by means of the passage 48 and passages 5!, 51, 58 and 59. If, however, either the body portion 44 is inclined to the vertical, the pendulum 5| being held in position by the force of gravity, or if the pendulum BI is affected by either acceleration forces or centrifugal forces,

thereby moving it with respect to the body portion 44! of the valve, the relative positions of the valve body and the pendulum will be as shown in Fig. 5, thereby closing the restricted passage 5i and hence closing the valve. As shown in Fig. l, the valve is adapted for connection to the T-coupling 36 so that the threaded portion 45 of the valve is screwed into the 'r-coupling and the threaded portion 45 is connectedto the pipe 35 by means of a coupling member 63a. 'Thus it will be seen that when the pendulum Ellis actuated, the passage to the interior of the gage easing H is closed and no liquid can pass from the tank l3 through the pipel'l to the pipe 39 and to the interior of the gage casing ll, although the passage between pipes 31 and 39 is unobstructed, thereby permitting the flow of liquid from the tank I! to the engine or fuel 7 pump through the supply pipe "a.

Referring now to Figs. 6, 7, 8 and 9, there is shown another form of a novel pendulum controlled valve adapted for use with the present invention, wherein the bushing 49 is provided with a relatively large opening in which an operating member having a substantially triangular crosssection is located, said member being provided with a valve head 64 which is adapted to be seated against a valve seat 55 formed at the bottom of the bushing 49. The edges of the member 53 are rounded as at 55, in order that they may fall flush against the internal surface of the bushing 49 as shown in Fig. 8. The sides 61 of the valve member, however, form passages 58 between said member and the bushing 49, which passages are closed when the head 64 of the valve member is forced against the seat 55 of the bushing 49. In order to operate the valve member 59 within the bushing 49 and against the valve seat 55, the spherical-shaped member or ball 52 is flattened at the top thereof as indicated at 69 so that when the pendulum 5| which operates the ball 52 is in a normal vertical position, as shown in Fig. 7, the valve member 63 is permitted to drop down from the bushing 49 and to rest on said flattened surface 59 thereby opening the passages 59 and providing a clear path through the valve, but when there is relative movement between the pendulum 5| andthe body portion 44 of the valve, the ball 52 operates somewhat like a cam, thereby raising the valve member 53 and causing the head 54 thereof to be seated-against the valve seat 55, thus closing the passages 58 and, hence, the valve. This form of valve is adapted for connection into the pipe-line in the same manner as theformshownv in Figs. 4 and 5 and operates in the same manner to close the passage to the interior of the gage casing If so that no liquid can pass thereto from the tank I 3.

In Fig. 3 there is illustrated still another embodiment of a novel valve which may be utilized with the invention, in which, however, the

pendulum is adapted for movement only about gravity when thevehicle is inclined upward or downward. In this embodiment, the valve is provided with a similar bushing 49 as in the form shown in Figs. 4 and 5 and having a restricted passage 5|. The latter, however, is adapted to be closed by meansof a ball 10 which normally rests on a support If. The ball 10 is adapted to be moved into a recess 12 provided at the bottom of the bushing 45 by a cam action of the ball 52 for which purpose said ball 52 is eceentrically pivoted within the lower end of the body portion 44, as by means of a pin I9 which extends through the ball 52 and is secured to the body portion 44 at points diametrically opposite each other. The ball 52 is actuated on its pivot 13 by means of the pendulum 5i and rod 60 in the same manner as in the valves shown in Figs. 4 to 7, inclusive. The closed position of the valve is shown in dotted lines in this figure and in this position the pendulum 6! is moved to the left as indicated at 5!.

There is thus provided a novel combination and arrangement including a liquid level indicator of the hydrostatic-cell type and venting means for the indicator and for the container ortank with which it is associated whereby, under certain extreme conditions as on an aircraft in inverted flight, liquid is prevented from entering the indicator from the container or tank.

Although several embodiments of a valve have dicator by claims for a definition of the limits of the invention.

What is claimed is: 1. In combination with a. fuel tank adapted to be carried by an aircraft having an instrument panel, a pressure responsive gage remote from said tank and adapted to be mounted on said instrument panel for indicating the quantity of fuel in said tank in accordance with the pressure-head of said fuel, said gage including a casing, an indicator, a pressure-responsive member in said casing, and means for actuating said inovement of saidpressure-responsive means, a hy rostatic cell immersed in the fuel in said tank to the maximum depth of the fuel, a pipe-line connecting said cell to said pressureresponsive means whereby pressures corresponding to the height of the fuel in the tank are transmitted to the gage, means including a second pipe-line connecting the tank and the gage casing to a common venting point, and means connected in said second pipe-line and controlled by forces of acceleration and gravity acting about either the transverse or the longitudinal axis of the aircraft for closing the connection between the tank and the gage casing to prevent passage of fuel into said casing due to acceleration of the aircraft and when said aircraft departs from level flight. 1

2. In combination with a fuel tank adapted to be carried by an aircraft having an instrument panel, a pressure-responsive gage remote from said tank and adapted to be mounted on said instrument panel for indicating the quantity of fuel in said tank in accordance with the pressure-head of said fuel, said gage including a casing, an indicator, a pressure-responsive member in said casing, and'nieans for actuating said indicator by movement of said pressure-responsive means, a hydrostatic cell immersed in the fuel in said tank to the maximum depth of the fuel, a pipe-line connecting said cell to said pressure-responsive means whereby pressures corresponding to the height of the fuel in the tank are transmitted to the gage, means including a second pipe-line connecting the tank and the gage casing to a common venting point, and means associated with said pipe-line and' controlled by forces of acceleration and gravity acting in any head of said fuel, said gage including a casing, an

indicator, a pressure-responsive member in said casing, and means for actuating said indicator by movement of said pressure-responsive means, a hydrostatic cell immersed in the fuel in said tank to the maximum depth of the fuel, a pipeline connecting said cell to said pressure-responsive means whereby pressures corresponding to the height of the fuel in the tank are transmitted to the gage, means including a second pipe-line connecting the tank and the gage casing to acommon venting point, and means associated with said second pipe-line and controlled by forces of acceleration and gravity for closing the connection between the tank and the gage casing to prevent passage of fuel into said casing due to acceleration of the aircraft and when said aircraft departs from level flight, said last-named means comprising a valve having a universally mounted pendulum associated therewith for controlling said valve irrespective of the direction of the acceleration forces and the direction of departure of the aircraft from level flight.

4. In combination with a hydrostatic fuel level gage for vehicles, a fuel tank adapted to be carried by the vehicle, means connecting said gage and tank for operating the former by the pressure-head of the fuel in the latter, means connecting the interior of said gage and saidtank to a common venting point, and a valve including a universally mounted pendulum for closing the connection between the interior of the tank and the interior of the gage-when the vehicle is accelerating or decelerating, or is inclined in any direction with respect to the horizontal.

CLARENCE LEE SEWARDJJR. 

